If you sleep six hours a night for twelve days, [Harvard neurologist and sleep medicine physician Josna] Adusumilli says — and that's about how much many Americans sleep all year round — your cognitive and physical performance becomes virtually indistinguishable from that of someone who has been awake for twenty-four hours straight. (The same effect is produced by six days of four-hour nights.) And the performance of someone who has been awake for twenty-four hours straight is similar to that of someone with a blood alcohol level of 0.1 per cent. In other words, "normal" amounts of sleep deprivation have us acting like we're drunk.

No matter what we do for a living, this affects our day-to-day performance at work and our relationships with others around us. And the physical and mental problems caused by lack of sleep are even scarier, including weight gain, memory problems, inability to perform, depression, increased cancer risk, and the buildup of proteins in the brain associated with Alzheimer's.

flickr/Craige Moore

Despite all this, people continue to insist that they are fine — post this story on Facebook and someone will invariably comment, "I get by on 5 hours a night just fine."

There's a reason for this, according to Charles Czeisler, another sleep specialist Konnikova spoke with. We're only able to tell that we're not performing at our best for a day or two. So if you get the Sunday blues and stay up watching Netflix or reading on your iPhone, and then you have a long day on Monday and an early meeting on Tuesday, you may have already settled into a sub-optimal performance routine for the week, compounding the negative effects of sleep deprivation every subsequent night.

Your brain just loses the ability to tell the difference.

People "who are chronically sleep deprived may no longer be capable of reliably appraising their own sleepiness — or they simply don't experience levels of sleepiness in any way commensurate with their actual deprivation," writes Mark Wolverton in Psychology Today, describing the research David Dinges of the University of Pennsylvania. You may feel a little bit sleepy — nothing more — but your body and your brain are just struggling to get by on such a severe deficit.

As Elizabeth Klerman, another sleep scientist, explained to Konnikova, "Why would you expect the brain to be able to police itself?"